Dual coil electric relay



Jan. 30, 1951 E. .1. RABENDA 2,540,022

DUAL ,com ELECTRIC RELAY Filed March 5, 194s AGENT Patented Jan. 30, 1951 DUAL COIL-ELECTBIC RELAY Edward J. Rabenda, Poughkeepsie, N. Y., asaignor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application March 3, 1948, Serial No. 12,851

1 Claim.

This invention relates to electromagnetic relays of the type used in electrical accounting machines wherein a plurality oi' such devices may be electrically connected in parallel.

It is common practice in record controlled electrical accounting machines to operate a plurality of relays and other electromagnetic devices some of which may be connected together electrically, in parallel, at one time or another due to the timed sequence operation of such machines. It is also common to have multicoil relays in such circuits wherein one coil of a,

relay is energized to pick up or attract an armature and another coil on the relay is used to hold or retain the armature attracted. Such arrangements are essential to the peculiar mode of operation requirements with such machines.

Normally the so-called dual coil relays are constructed having two coils wound upon the same core, in some relays with one coil wound over the other and in others with the windings abutting each other. Usually the impedance and ampere-turn ratios of these windings are arranged so that one coil, known as the pick-up coil, when energized, attracts the armature in a very short period of time, while the coil, known as the holding coil, when energized, retains the armature attracted. I'hese characteristics are required in their use with electrical accounting machines due to the circuit complexity and rapidity of operation of such mechanisms. For the same reason the pick-up and holding coils of a specific relay frequently are connected in parallel with similar coils in other relays, or with dissimilar coils, or with other closed circuits.

It has been found that where dual coil relays are connected to have one or the other of their windings in lparallel in the manner described above, certain deleterious eil'ects may result. For example, where a holding coil is connected in parallel with another holding coil the pick-up coil has been found to function sluggishly in attracting its relay's armature. Conversely, where a pick-up coil is connected in parallel with another pick-up coil, it has been found that when the holding coil of the relay releases the armature time has been required. In the last mentioned situation there is also a tendency for the second mentioned relay pick-up coil. to be energized by the cle-energizing of the holding coil oi the first mentioned relay. The phenomena just observed are traceable to the transformer action inherent in dual coil relays and to the circulating currents set up therein under certain circuit conditions arising in the operation of very high speed electrical accounting machines.

The primary object oi this invention is to provide an improved dual coll relay device wherein the mutual inductive relationship between the coils is reduced to a minimum.

A further object of this invention is to provide a dual winding electromagnet wherein the mutual reluctance of the common magnetic paths is increased to a maximum.

Other objects of the invention will be pointed out in the following description and claim and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawing:

Fig. l is a front elevation View of the invention.

Fig. 2 is a diagrammatic view oi' the magnetic flux distribution in a conventional type dual coil relay.

Fig. 3 is a diagrammatic view of the magnetic flux distribution in a dual coil relay of the type disclosed in the present invention when the relay armature is iirst attracted by the pick-up coil being energized.

Fig. 4 shows the magnetic ux distribution in a relay of the type herein disclosed when both the pick-up and holding coils are energized.

Fig. 5 illustrates the magnetic ilux distribution in a further modication of the present invention as applied to a dual coil relay having its armature closed and both the pick-up and holding coils being energized.

Referring now to Fig. l, a coil ill and a coil Il are mounted respectively upon the legs l2 and I3 of a relay magnetic core I4 having a third leg 15 at one end of which is pivotally fastened an armature I6. The armature il is connected by a link I1 to a movable contact member IB. With the arrangement of the coils Il and Il as shown the interlinkages of magnetic iiux via the core and via stray flux paths are reduced;.this feature, however, is best illustrated by reference to Figs. 3, 4, and 5.

Fig. 2 illustrates the flux distribution in a conventional relay having a pick-up coil P, a holding coil H, a core C, and an armature A pivoted on the core C by a pivot Q. In this type of dual coil relay the magnetic flux set up by energization of either the pick-up coll (dash dot lines) or the holding coil (dash lines) passes through the magnetic path of the other coil,

including even a part of the stray nux paths of each coll. It is obvious that transformer action occurs in relays of this type in the manner previously described.

Fig. 3 shows the flux distribution in a dual coil relay according to the present invention, wherein a magnetic core C has a leg M about which is wound a holding coil H. a leg L about which is wound a pick-up coil P, and a leg K to one end of which an armature A is pivoted by a pivot Q, the armature A being in its normally open position. Flux set up by the pick-up coil P (dash dot lines), except for stray flux, is principally confined to the leg L, part of the coreC, the leg K, and the armature A, little or none of this flux being interlinked with the holding coil H. Conversely flux set up by the holding coil H is principally confined to stray flux and the return path of leg Ml little or none of the ilux being inter linked with the pick-up coil P due to the high reluctance of the air gaps between leg M, leg L, and armature A. When, however, the armature is closed, as shown in Fig. 4, interlinkage of the magnetic flux of coil P with coil H does occur, and vice versa. 4In this instance, however, an alternate flux path is provided in either event by the leg K so that the flux passing through either coil as a result of the others being energized is proportionately reduced. Consequently the transformer action in the mode of the present invention illustrated in Figs. 3 and 4 is reduced considerably'over that occurring in a conventional type relay such as illustrated in Fig. 2.

It has been found that a considerable influence is exerted mutually between the holding and pickup coils by the stray flux. For purposes of clarity the diagrams of Figs. 2, 3, and 4 have not been drawn to showthe stray flux influence. The arrangement of the coils I and Il, however, as shown in Fig. l, is such that the pick-up coil I0 is placed at one end of the leg- I2 while the holding coil II is placed at the opposite end of the leg I3. This separation of the pick-up and holding coils in an arrangement as in the present invention has the effect of further reducing the mutual flux path and hence the transformer action between the coils.

Fig. 5 illustrates a further modification of the subject invention wherein a core C has a leg M about which is wound a holding coil H, a partial leg L about which is wound a pick-up coil P, and a leg K to one end of which is pivoted an armature A by a pivot Q, the partial leg L being attached to the core C by a non-magnetic portion B. The non-magnetic portion may be inserted in a relay of the type shown in Fig. 1 as a portion of the leg I2 lying between the reference lines u Number 4 a-b. With the arrangement of Fig. 5, practically no mutual nux path between the coils H and P exists, and similarly little, if any, transformer'action is obtained since the flux as a result of coil P (dash dot lines) consists principally of the stray ux and return path of the armature A and the leg- L while the flux resulting from the coil H (dash line) is largely confined to stray ux (separated physically from influencing coil P) and the path composed of leg M, core C, leg K, and armature A. The flux from the coil H is further isolated from influencing coil P when the armature A is in its normally open position as in Fig. '4.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claim.

What is claimed is:

An eiectromagnet having a U-shaped core of a predetermined cross-section and a second core of a substantially greater cross-section central thereof and parallel with the arms of the first said core, the ends of all said cores forming the pole faces of the said magnet, an armature extending over the said pole faces, a lumped winding on one of the said arms and located at the bottom ofthe said U-shaped member, and a second lumped winding on the said second core located at the pole face thereof, whereby the stray flux effect of the first said winding relative to the said armature is reduced to a minimum and the stray flux eifect of the second said winding is increased to a maximum.

EDWARD J. RABENDA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Erickson June l, 1920 Whittingham Apr. 1, 1930 Eiseman June 24, 1930 Madsen Dec. 1l, 1945 FOREIGN PATENTS Country Date 44,820 France Apr. 15, 1935 (Addition to No. 777,939)

Clausen Mar. 3, 1914 

